Ammonium dinitramide is a non-chlorine containing oxidizer useful in rocket propellant and gas generating devices such as air bag inflators. For example, in U.S. Pat. No. 5,324,075, ammonium dinitramide is described as a preferred gas generator for air bags. In U.S. Pat. No. 5,316,749, a process for producing stable ammonium dinitramide salts is disclosed for use in a smokeless rocket propellant. While ammonium dinitramide compounds have useful functional properties, they suffer from physical limitations which renders their use impractical.
For example, ammonium dinitramide ("ADN") crystallizes naturally in the form of needles or plates which are not readily amendable to subsequent processing. For use as a propellant or gas generator, it is necessary to use solid particulate ammonium dinitramide of controlled size to obtain predictable results. Particles in the range of about 10 to 1,000 microns are considered useful. However, efforts to control crystallization or to physically process solid ADN to obtain a selected particle size have been unsuccessful, as solid ADN cannot be ground or subject to other physical processing due to its low stability.
One method for producing particulate ammonium dinitramide is to melt ADN in a non-solvent fluid, vigorously stirring to disburse the ADN, then rapidly cooling the mixture before the melted ADN coagulates.
This process is not suitable because melted ADN can decompose violently if it remains melted for too long a period of time. Also, to minimize the potential damage if decomposition were to occur, the total amount of ADN in the fluid must be minimized. While possibly adequate for producing laboratory size quantities of ADN, such a method cannot be used to produce the large quantities of material necessary, i.e. for use as a propellant.